Effect of RF sputtering power on morphological and electrical properties of calcium copper titanate thin films

Abstract

dielectric constant, but these are limited to low temperature applications. Beyond the Curie temperature (T c ) their dielectric properties decreases dramatically, which is undesirable for device applications. Recently, CaCu 3 Ti 4 O 12 (CCTO), possessing a distorted cubic perovskite structure, has received intensive consideration due to its extraordinary dielectric behavior [7]. The dielectric constant of CCTO ceramics is in the order of 10 5 over a broad range of temperature due to its stable cubic structure [8] and also no lattice distortion has been observed in CCTO between this temperature range as confirmed by neutron diffraction and high resolution X-ray diffraction [7,8]. The origin of high permittivity in CCTO is still under debate. High dielectric behavior is the common feature in ferroelectric materials. In case of CCTO, the contribution from dipoles has been ruled out due to its centrosymmetry nature even at low temperature [7,8]. The internal barrier layer mechanism is widely accepted for explanation of giant dielectric permittivity in CCTO, where the conducting grains are separated by insulating grain boundaries [9]. Application of CCTO in microelectronics for memory devices, sensors, capacitor and varistors demands the deposition of CCTO thin films on silicon substrate.Due to the unique dielectric behavior of CCTO bulk ceramics, many research groups have initiated deposition of CCTO thin films by different deposition techniques [10-16] on various types of substrates [17][18][19]. Sputtering is considered as one of the most promising deposition technique for thin film deposition [20]. There are very few reports of deposition of CCTO thin film by RF sputtering [12,21]. Sputtering parameters like RF power, deposition pressure, substrate temperature strongly influence the structural, morphological and electrical properties of thin films. In our previous work [22], we have deposited CCTO thin film with the variation of deposition pressure on silicon Abstract Calcium copper titanate (CCTO) thin films were deposited on p-type silicon substrate by RF magnetron sputtering at various RF powers. Post deposition annealing was carried out for all the samples at 950 °C for 1 h in air atmosphere. Various types of surface morphology have been observed for CCTO thin films with the variation of RF power. The evolution of polycrystalline structure of the CCTO thin films was confirmed by XRD studies. The FTIR characteristic absorption band of CCTO was observed in the range of 400-700 cm −1 . The capacitancevoltage (C-V) and current-voltage (I-V) characteristics of the films were investigated employing Al/CCTO/Si MOS capacitors. CCTO films with higher dielectric constant, lower oxide and interface charge density were obtained at higher RF power. Leakage current was also found to be minimum for RF power of 105 W.